i) Field of the Invention
This invention relates to a print head which prints by driving print wires that are fixed on the free ends of respective armatures, and also to a process for fabricating the print head. In particular, this invention is concerned with a print head which includes an annular permanent magnet that is formed by a combination of split segments, and also with a process for making the magnet.
ii) Description of the Related Art
Impact printers of the type in which print wires are driven to strike a printing medium via an ink ribbon and printing is performed by the striking force are used in a wide variety of fields, led by output devices in information processing systems, owing to high freedom in the printing media that can be used and relatively low price.
Depending on the designs of their wire print heads, these impact printers can be classified into three types: the plunger type, the spring charge type, and the clapper type.
The spring charge type of print head has armatures with corresponding wires fixed thereon. The armatures are supported by respective biasing leaf springs, and normally attracted to respective cores against the resilient forces of the associated biasing leaf springs by a permanent magnet. During printing, a coils wound on the cores are energized to produce a magnetic flux in a direction opposite to that of the permanent magnet and hence to release the associated armatures. There has been an ever increasing demand for speeding-up the printing process in recent years so that wire print heads of the spring charge type, which feature good high-speed response, have been extensively adopted.